This paper investigates regime shifts in the wintertime Siberian High central intensity for the period from 1950 to 2017. One regime shift was found from a test for multiple regime shifts. A Markov switching model analysis identified the period of 1950-1987 as a strong intensity regime, 1988-2017 as a weak intensity regime, and 1987-1988 as the changepoint. We also found a regime shift in the wintertime temperature in Asia, which is consistent with that in the intensity of the anticyclone. The periods of 1950- 1986 and 1988-2017 are a low and high temperature regime, respectively, and the changepoint is 1986-1988.

In the present study, changes in the activities of typhoons in the early typhoon season (April-June) in relation to the intensity of Siberian anticyclones and large scaled atmospheric circulations that cause those changes were analyzed. In years of positive Siberian anticyclones, typhoons occurred in the western waters of the subtropical western Pacific and went through the South China Sea to move toward the ashore to the southern coast of China or came north from the deep sea on the southeast of Philippines, changed directions and moved to the deep sea on the east of Japan. In years of negative Siberian anticyclones, typhoons occurred in the western waters of the subtropical western Pacific, went through the East China Sea and changed directions to move toward Korea and Japan. These differences between the two years were identified through stream flow differences at 850 hPa and 500 hPa between the year of positive Siberian anticyclones and the year of negative Siberian anticyclones. In both analyses, the cold northeasterly anomalies formed because anticyclonic circulation anomalies were centered on the Sea of Okhotsk and cyclonic circulation anomalies were center on the middle-latitude waters of the northwestern Pacific affected the Republic of Korea and Japan. Therefore, the cold northeasterly anomalies played the role of steering flows to prevent typhoons occurred in the subtropical western Pacific from moving toward Korea and Japan in years of positive Siberian anticyclone indexes. In particular, according to the analysis of stream flow at 850 hPa, cyclonic circulation anomalies were reinforced in the western waters of 140°E in the subtropical western Pacific and anticyclonic circulation anomalies were reinforced in the eastern waters of 140°E in the subtropical western Pacific and thus the former waters provided good environments for the occurrence of typhoons in years of positive Siberian anticyclone indexes and the latter waters provided good environments for the occurrence of typhoons in years of negative Siberian anticyclone indexes.